The author makes an analysis and presentation of the doctrine of police powers of the administration and the doctrine of the public intervention in the economic order that are base for the development of new regulation that, due to its effects, could be quoted as expropriatory of foreign investments protected by bilateral investment treaties (BIT) and Free Trade Agreements (FTAs). The author shows the tendency of the international Tribunals in this respect, centering his attention in the study of the regulation and the clause of expropriation as a limit of the police powers of the administration. Before approaching these points, the author studies the economics of foreign investment and expropriation. Later, he develops a Law and Economics analysis of indirect expropriation as a limit of the prescribed power and the police powers of the administration and finalizes with a reflection on the limits of regulation and public intervention by means of regulation, indicating that not only the expropriation clause constitutes a limit to regulation but also the clause of fair and equitable treatment present in all BITs.